Naturally scented cleaners have unexpected risks

What cleans, is naturally scented, and has unexpected health risks? Cleaning products containing pine, lemon and orange oils. These chemicals, used as solvents and as scents, are members of the “terpene” family. Cleaning products containing terpenes were the focus of a four year study into the potential hazards of everyday cleaning products designed for household use.

"We've focused a lot of effort in the last decades on controlling the big sources of air pollution and on the chemicals in consumer products that contribute to outdoor ozone formation. However, now we've learned that we need to pay attention to other aspects of pollution sources that are right under our nose," said William Nazaroff, the study’s lead author.

Nazaroff is a professor of environmental engineering at the University of California, Berkley.
The study also examined products containing ethylene-based glycol ethers, used as a solvent in a wide range of cleaning products. The researchers studied 21 products, including four air fresheners, and a cross-section of other cleaners including disinfectants, general purpose cleaners, spot removers, furniture polishes, wood cleaners, general purpose degreasers,and multipurpose solvents.

Researchers studied what happened when these everyday home cleaning products were used in normal conditions according to instructions. When the researchers tested the terpene-containing products in the presence of ozone, they found that the substances reacted to produce formaldehyde, a respiratory irritant that is classified as a human carcinogen. They also produced very small particles with properties like those found in smog and haze, as well as other oxidation products. The amounts of terpenes that were converted into these pollutants depended on the amount of ozone present.

Ozone occurs naturally in the air around us. It is also generated by some home appliances, including computer printers, ionizing air cleaners and ozone generators.

Products were tested in a variety of realistic use scenarios. Some scenarios showed that people could be exposed to potentially dangerous levels of toxic pollutants from this one exposure alone.

  • Cleaning scale off a bathroom stall for 15 minutes in a small, moderately ventilated bathroom exposed the person to three times the acute one-hour exposure limit for glycol ether set by the California Office of Environmental Health Hazard Assessment.

  • A person who cleans four houses a day, five days a week, 50 weeks per year would take in about 80 micrograms of formaldehyde daily. This is double the guideline value in California. In addition, the person's intake of fine particulate matter in those hours alone would exceed the federal guideline for particulate matter for an entire year. That’s without all the other exposures to formaldehyde or fine particulate matter during non-work hours.

  • If air fresheners and ozone generating devices are used simultaneously in a child’s bedroom, the child would be exposed to formaldehyde levels 25% higher than California’s guidelines. The report notes that because other sources of formaldehyde may be present, exposure to formaldehyde could be even greater.

Products varied widely in the amount of terpenes and ethylene based glycol ethers they contained. Of the four air fresheners studied, three contained what researchers labeled “substantial amounts” of terpenes - 9-14% by mass. Twelve of the 21 products studied contained terpenes and other ozone-reactive compounds at levels ranging from 0.2 to 26 percent by mass. Six products contained levels of ethylene-based glycol ethers of 0.8 to 9.6 percent by mass.

The study is the first to measure the hazardous byproducts produced through normal use of common cleaning chemicals, and to evaluate the risks of these exposures.

The take home message from these studies, according to Nazaroff, is that people need to be cautious about overuse of products containing these substances. Nazaroff encourages consumers to buy scent free cleaning agents, and to beware of deceptive advertising. “What is advertised as being organic and green and good for us isn’t automatically so,”Nazaroff warns.

Consumers can identify many products containing terpenes, as most advertise their “fresh lemon scent”, “smell like a pine forest,” or “natural orange cleaning power.” Avoiding ethylene based glycol ethers is more difficult, as few cleaning products list ingredients on their labels.
The study was funded by the California Air Resource Board. It can be viewed online at